Reduction of metallic oxids and the like.



' F. w. HIGHFIELD.

THE REDUCTION OF, METALLIC OXIDS AND THE LIKE. APPLICATION FILED MAR. 15, 1915.

1,153,786 PatentedSept. 14, 1 91.5.

2 SHEETS-SHEEP".

BEST AVAILABLE COPY F W HiGHFiELD.

TH: REDUCUGN 0F METALLIC OXIDS AND THE LIKE.

APFLECAHGN Hi5! MARIN). 9:5- fiijl ifigafib Patmted Sept. 14, 1.915.

UNITED ,sra'rns PATENT ()EElGE.

FRANK WILLIAM HIGHI'IELB, 01E GAVERSHAM, ENGIAIilD.

' REDUCTION 01B METALLIC OXIDS AND THE LIKE.

Specification of letters Eatcnt.

Patented Sept. 14, 1915.

Application filed March 15, 1915. Serial No. 14,453.

To all whom it may concern: Be it known that I, FRANK lVILLrAM :HIGIIFIELD, a subject of the King of England, residing at Caversham, Oxford, England, have invented certain new and useful Improvements in theReduction of Metallic Oxids and the like, of Which the following is a specification. I

This invention relates to the reduction of metallic oxids and the-like, and in particular to a process and apparatus for the reduction of zinc oxid and the like by elec-' trical means. i

The process and apparatushavc been in vented primarily for theredu'ction of zinc eficiency and success of the. processes propo'sed.- g y The process according to the-present nvention does not propose to treat material other than zinc oxid or blue powder, for

by starting the true reducing process with this material a serious factor of diiliculty is eliminated. i

Another factor that gives rise to difficulty and has prevented success in some methods heretofore proposed, in the reduction of ainc oxid, is the extremely low vapor pressure of the metal, which low vapor pressure necessitates the employment of as large a condensation" surface as possible so asto promote the collection and conglomeration of condensed metallic globules. Other factors whiclthave to be carefully provided for are (el that the temperaturemust be very closely-under control since otherwise the reaction will not be completed, (6) the zinc vapor must be in very intimate contact with the hot, carbon in order that the reaction may proceed rapidly, (c) the at r mosphere Where the reaction is carried on,

that is to say in the region of contact with the hot carbon, must be an atmosphere of pure carbon monoxid; if it is impure there is a loss of metal, but, what is probably more important, isthat the prominent impurity will be carbon dioxid. This is heavier than the monoxid and therefore displaces the latter gas, driving it upward. Upward displacement of the monoxid means that the reduclng zone of the furnace has moved upward and this is objectionable for obvious reasons.

I f the heat of the carbon is maintained malnly or exclusively from ordinary combustion thereof by the admission of air or "ogrygen, the temperature developed at the surface of the carbon is usually too high for efiicient operation of the furnace since it is so high asto very largely prevent the condensation of the zinc vapor.

' According to the present invention, therefore, I provide a process for the recovery of ZlIlO from its oxid or'from blue powder [whereby the oxid or powder is fed on to the glowing surface of a bed of electrically heated carbon in an atmosphere of substan- 7 .tially pure carbon 'monoxid and the thereby reduced and condensed metal is allowed to percolate by, gravity through the said bed of carbon and is collected beneath the said carbon; after having been collected and before it is passed to the open air the metal is prehmmarily cooled in a neutral or a reducing atmosphere. The process is, according to this invention preferably carried out in a i:'urnace pro- 8 vided With a septum thatis heated by the furnace, is porous to carbon .monoxid at the Working temperature of the furnace and that divides the metallic oxid from an atmosphere of carbon monoxid derived from the said electrically heated carbon. The

septum conveniently takes the form of the Wall of a tube employed to direct the oxid on to the bed of carbon.

A form of furnace constructed according 9 to this invention for the reduction of zinc oxid is illustrated in the accompanying drawings, in which y Figure lie a transverse vertical section through the furnace on the line 1-1 of.

Fig. 2; and Fig. 2 is a vertical longitudinal central section through the furnace.

The furnace proper is seen at-A and is provided with an extension B to form a cooling chamber for the metal? A conical 106 feed hopper C .is provided at the top of the furnace and deliversthe oxid to a conduit or pipe D formedof firccl'ay so that its Wall may beporous toCO. This conduit is hereinafter called the condensation tube. 11c

Within the upper end of the tube D there is l a feed screw by which the oxid is fed .down into the furnace from the hopper.

- The furnace chamber A is oblong in plan,

and in its two short side walls are electrodes E of carbonwhich pass right through the walls. Beldw the open' bottom of the tube D, is a grate]? Whose bars are of firecla'y;

qlower end in a portion A that isf o theymay, however, be of iron if desired:

The furnace chamber terminates at e as an inverted pyramid that consti utes what may be termed the hearth of the furmedium.

nac'e. a:

From below the'hearth,a conduit G communicates with the cooling chamber B. This is traversedby a number of partitions or .ribs B* and these, as well as the end walls; -of this chamber are pierced with pipes B for the circulationof air or other cooling .with a sufficiently extended base to make a contact with both the. electrodes. .Current is then turned onto the electrodes, and the the current. The carbon forms at the moheap of carbon thus brought to a glowing condition by the. heat generated in it'by 'ment of first starting the furnace a certain small proportion of 00 but in the mainforms CO. The zinc oxid is then fed into' the hopper, and allowed to enter the furnace, by the operation of thescrew conveyer at the base of the hopper.

ably, (and probably in greater importancelf The coke is so disposed'as to cause the hottest part of the furnace to be at the walls- .40

in the neighborhood of 1050 C. butshould of the tube D. The temperature should be not greatly exceed this value. The. reactions probablyare as follows:

0+z'no=co+zn=. at .the temperature employed then probwhereupon the CO is itself reduced to CO.

The walls of the tube D are porous to CO, and this fact, coupled with the porous characterof the coke, serves to provide a large surface for condensation, inrelation to the volume of thefurnace. The large surface referred to is constituted in part by that of the coke and in part by that of the in:

terstices; of the tube. wall. -.Ow ing to .the-

extremely sm'all vapor pressure of zinc oxid this large condensation surface is peculiarly advantageous where zlncis {being recovjered. Further, since the hottest part of the furnace is at the tube D, any CO formed is immediately reformed in'to CO,

charcoal is piled upon the means.-

' describe the combined actions of condensation, and of running together of condensed globules or possibly of these actions inseparable. from and therefore combined with that of reduction. I. have found that this combined'acti'on takes place under the conditions'herein set forth, with greater completenessand with more readiness than under other heretofore employed conditions.

narily accepted and simple manner merely upon temperature nor merely upon the joint effects of temperature and ressure.

Afvery small quantity o blue owder is likelyto be formed at' the start, ut when short time. all CO will have been reduced, -'and the :condition essential for the reduction without-the formation of blue powder, namel glowing carbon in an' atmosphere of pure 0,. will have been reached.

the" furnace has been in operation for a 'It does not appear to depend in the ordi The reduced metal in a liquid condition. I

the fire-bars, and is collected in the hearth beneath. From here it passestothe cooling chamber, the provision of which is desirablewith zinc, in order'to preventthe metal reaching the open airat a temperature so high as to cause a ready oxidation.

except for the inlet and outlet for metal, and may conveniently befilled withnitroen or other inert gas when starting. If t is be not done, .andthe chamberbe full of .air, the. metal will' be oxidized by the oxygen-present, until this be exhausted, but the said useof nitrogen inthe chamber at the. start --will prevent the formation even of this smallquantity of oxid.

, Doors are provided in. the usual manner for cleaning the furnace and for'feeding in coke I asrequired but such ,doors are not shown in the drawings. f I WhatI claim as my invention and desire to secure by Letters Patent is:-5-

1. In a furnace for the recovery of zinc from an oxidized condition thereof, the compercolates through the glowing carbon past 100 The cooling chamber is completely closed bination of; a wall of material that is porous cooling chamber in direct communication with the said receiving chamber.

2. In a furnace for the recovery of zinc from zinc oxid, the combination of a feed tube Whose Wallis porous to: carbon monoxid at the Working temperature of the furnace and which is supported to be immersed in an atmosphere of pure carbon monoxid and to have its delivery end in contact With the upper surface of a body of porous carbon, means to heat the saidbody electrically, a grate Within the furnace upon Which the body of carbon is supported, a chamber beneath the grate to receive the reduced metal and a cooling chamber in direct communication with the said receivingchamber, but sealed from the open air.

3. In a furnace for the recovery of zinc from an oxidized condition-thereof, the com- :bination of a feed tube whose wall is porous to carbon monoxid at-theworkingtemperge ture of the furnace and which is supported to have its delivery end in contact with electriczilly heated carbon upon a grate Within the furnace, means within the feed tdbe to propel the material therethrough, a

chamber beneath the grate to receive the re- I duced metal and a cooling chamber in direct communication with the said receiving chamber.

4:. In a furnace for the recovery of zinc from an oxidized condition thereof, the combination of porous material supported in .with the said receiving chamber and having dOWIYWM'dlV depending projections from its roof pierced by conduits for the circulation of a cooling medium and provided with a liquid seal. at the outlet for metal.

In testimony whereof I have signed my meme to this specification in the presence of two subscribing Witnesses.

FRANK WILLIAM riieririELn.

Witnesses:

HAROLD H. SIMMQ'NS, HARRY B. Screen.

the hottest part of the furnace, a grate 

